High-frequency surgery has been used for many years in both human and veterinary medicine in order to coagulate and/or cut biological tissue. With the aid of suitable electrosurgical instruments, high-frequency current is conducted through the tissue to be treated, so that said tissue changes due to protein coagulation and dehydration. In the process, the tissue contracts such that the vessels become closed and bleeding is stopped. A subsequent increase in the current density brings about explosive evaporation of the tissue fluid and tearing open of the cell membranes, so that the tissue is fully parted.
Both bipolar and monopolar techniques are used for the thermal treatment of biological tissue. In the case of monopolar arrangements, the high-frequency current fed from the high-frequency generator to the electrosurgical instrument is applied to the tissue to be treated via a ‘different’ electrode, wherein the current path runs through the body of a patient to an ‘indifferent’ neutral electrode and from there back to the high-frequency generator. A high current density per unit area is provided at the ‘different’ electrode for the treatment, whereas at the ‘indifferent’ electrode, the current density per unit area is significantly less compared with the ‘different’ electrode. This can be achieved with a suitably large area configuration of the neutral electrode. This arrangement ensures that no injuries, such as burns, occur in the tissue at the interface between the tissue and the neutral electrode.
In order to perform a coagulation, a high-frequency surgical apparatus is used which comprises an high-frequency surgical device with an high-frequency generator to create a high-frequency voltage or a high-frequency alternating current, as well as switching equipment and/or control and regulating equipment for activating or deactivating, or more generally for controlling the high-frequency generator.
For the safety of the patient, provision should be made, during a procedure, for constantly checking whether the neutral electrode is operating correctly and, for example, is properly placed on the patient. Any detachment of the electrode leads to a dangerous increase in the current density at the regions which still adhere, so that the injuries mentioned above could possibly occur. In order to ensure a high degree of safety for the patient, monitoring circuits are used which, for example, test the adhesion of the neutral electrode on the patient. Neutral electrode monitoring circuits of this type in a high-frequency surgical apparatus typically determine the transition resistance and/or the current distribution between the two conductive segments of the neutral electrode. Conclusions are often drawn concerning possible heating of the electrodes from these measured values. However, these conclusions are only relevant if electrode-specific parameters, such as area, geometry and structure of the electrodes are known. Particularly problematic in this context is the evaluation of very small neutral electrodes such as those sold for use with babies and small children. These can only be operated with a reduced high-frequency current strength since otherwise the heating can reach unacceptably high values. Also problematic herein is assessing neutral electrodes for their ‘operating behavior’.
It is therefore an object of the disclosed embodiments to provide a high-frequency surgical testing device which not only enables this evaluation and assures a high level of safety both for the patient and the surgeon when using a neutral electrode and but also is as easy to use as possible.